Long-Bailey said that the agency would “create thriving businesses within our communities, bringing life back to local economies” via a network of business advisers operating out of larger Post Bank branches to provide guidance for local businesses on how to access support and finance.

It would also promote the use of small and medium-sized enterprises across government, helping them to access government contracts so that they could better compete with larger businesses, and create a central, online portal for business support.

Other pledges in Labour’s business plan included scrapping quarterly tax reporting for businesses with a turnover of under £85,000, through ending the requirement in HM Revenue and Customs’ Making Tax Digital rollout. It would also give business more flexibility over how they use the apprenticeship levy, including the option to use it for all accredited training schemes.

Announcing the 20-point plan, Long-Bailey said: “Small businesses, the lifeblood of our economy and our communities, are being stretched to breaking point by global corporations that evade their taxes and fail to pay their suppliers on time. This inequality scars our country.

“Small businesses are vital to a thriving economy. Labour wants business support and finance to be available for entrepreneurs from the moment the seed of an idea is planted.”

Responding to the announcement on behalf of the Conservatives, international trade secretary Liz Truss said: "Despite what they claim, Labour are not on the side of small businesses.

She added that smaller companies "don't need a new quango, they need certainty".

"All Corbyn's Labour will bring is higher taxes and uncertainty with no plan for Brexit".

The Liberal Democrats' business spokesperson, Sam Gyimah, said: "Labour under Jeremy Corbyn has dropped any pretence of being friendly to industry, returning to plans from the 1970s to take over company shares and nationalise swathes of the economy."

He also accused both Labour and the Conservatives of being united by Brexit, "the most anti-business policy of all".